1. Technical Field
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device and a method of fabricating the LCD device.
2. Description of the Related Art
Presently, LCD devices are being developed as the next generation of display devices because of their light weight, thin profile, and low power consumption. In general, an LCD device is a non-emissive display device that displays images using a refractive index difference utilizing optical anisotropy properties of a liquid crystal material that is interposed between an array (TFT) substrate and a color filter substrate. Among the various type of LCD devices commonly used, active matrix LCD (AM-LCD) devices have been developed because of their high resolution and superiority in displaying moving images. The AM-LCD device includes a thin film transistor (TFT) in each pixel region as a switching device, a pixel electrode in each pixel region, and a second electrode used for a common electrode.
FIG. 1 is a schematic cross sectional view of an LCD device according to the related art. In FIG. 1, an LCD panel 1 includes upper and lower substrates 5 and 22 arranged to face each other with a liquid crystal layer 14 interposed therebetween. A color filter layer 7 and a common electrode 18 overlie an inner surface of the upper substrate 5, in which the common electrode 18 functions as an electrode for applying an electric field to the liquid crystal layer 14. The color filter layer 7 includes red, green and blue color filters 7a, 7b and 7c for passing only a specific wavelength of light, and a black matrix 6 that is disposed at the boundary between the red, green and blue color filters 7a, 7b and 7c and shields light from a region in which alignment of the liquid crystal layer 14 is uncontrollable. On an inner surface of the lower substrate 22, a gate line 13 and a data line 15 cross the gate line 13 to define a pixel region P. A TFT T, which functions as a switching device, is disposed at crossing of the gate line 13 and the data line 15. The TFT T includes a gate electrode 32 connected to the gate line 13, a semiconductor layer 34 over the gate electrode 32, a source electrode 36 connected to the data line 15, and a drain electrode 38 spaced apart from the source electrode 36. A pixel electrode 17 is connected to the TFT T. For example, the pixel electrode 17 is made of a transparent conductive material such as indium tin oxide (ITO).
A portion of the gate line 13 is utilized for a first capacitor electrode (not shown). A second capacitor electrode 30 is formed with the same material as the data line 15. The first capacitor electrode, the second capacitor electrode 30 and a gate insulating layer 33 interposed therebetween constitute a storage capacitor CST. Here, the second capacitor electrode 30 is connected to the pixel electrode 17 to be applied to a signal of the pixel electrode 17.
A structure of the storage capacitor CST may be variously modified.
In addition, a backlight unit 50 is disposed under the LCD panel 1. The backlight unit 50 includes a cold cathode fluorescent lamp 52 as a fluorescent lamp, a lamp housing 54 covering the cold cathode fluorescent lamp 52, a light guide panel 56 that converts light from the cold cathode fluorescent lamp 52 into a plan light, a reflector (not shown) under the light guide panel 56 to reflect light toward the LCD panel 1, a diffusion sheet (not shown) diffusing light from the light guide panel 56, first and second prism sheets (not shown) controlling a direction of the light for the first diffusion sheet, a protection sheet (not shown) protecting the sheets therebelow.
However, the LCD panel 1 is increasingly being manufactured as a light-weight, slimly-shaped, model, for example, such that a light emitting diode is suggested instead of the cold cathode fluorescent lamp 52 as the light source of the backlight unit 50.
The light emitting diode can emit red, green and blue colors and can be manufactured as a small, slim and a light-weight device.
In addition, a field sequential color (FSC) driving method is suggested to obtain a high image quality with respect to an LCD device using a backlight unit having the mentioned light emitting diode emitting the red, green and blue colors. This FSC driving method may be defined such that red, green and blue colors are sequentially embodied and mixed with a time interval among the red, green and blue colors, thereby improving brightness in comparison with the related art driving method. Actually, in the FSC driving method, inputting data and the response speed of the liquid crystal material should be faster than the driving method according to the related art, which will increase brightness. However, there is a limitation to increasing brightness because the on-time of the backlight unit, except for inputting data and response time of the liquid crystal material, is limited.
To overcome these limitations, a tiling driving method, which is defined such that the LCD panel is independently driven in accordance with partitioned portions, is suggested.
FIG. 2 is a schematic plan view of an LCD device applying a tiling driving method according to the related art.
As shown in FIG. 2, an LCD device 70 includes an active area A1 displaying a picture and a driving area A2 in a periphery with the active area A1. The LCD device 70 is partitioned top, bottom, right and left portions with respect to central line CL. Accordingly, as first and second source integrated circuit boards 72a and 72b are disposed in both the top and bottom portions and first and second gate integrated circuit boards 74a and 74b are disposed in the left portion, they are independently driven by the partitioned portions.
More specifically, the first and second gate integrated circuit boards 74a and 74b in the top and bottom portions with respect to the central gate line (not shown) are independently driven and scanning of the gate lines is begun from the central gate line. Here, top and bottom pixels of the central gate line are sequentially driven simultaneously.
As explained above, when the LCD panel is independently driven by the partitioned portions the inputting time of the data is reduced. Therefore, the response time and on-time of the backlight unit have an enough margin due to the reduction of inputting time.
Consequently, the LCD device applying the FSC driving method using partitioned driving can obtain high brightness.
FIG. 3 is an expanded plan view of a substrate of a FSC type LCD device applied a tiling driving method according to the related art.
As shown in FIG. 3, a plurality of gate lines 82 and 82a and a plurality of data lines 84 cross the plurality of gate lines 82 and define a plurality of pixel regions P on a substrate 80. For example, the substrate 80 is made of a transparent insulating material. A plurality of thin film transistors T, T1 and T2 are formed at crossing points of the plurality of gate lines 82 and 82a and the plurality of data lines 84 and are symmetrically formed with respect to a central gate line 82a of the plurality of gate lines 82 and 82a. Each of the plurality of thin film transistors T, T1, T2 includes a gate electrode 86, a semiconductor layer 88, a source electrode 90 and a drain electrode 92.
Here, the first and second thin film transistors T1 and T2 of the plurality of thin film transistors T, T1 and T2 are connected to the central gate line 82a.
Each of a plurality of pixel electrodes 94 is connected to the each of the plurality of the drain electrodes 92. In other words, the first and second thin film transistors T1 and T2 adjacent to the central gate line 82a are all connected to the central gate line 82a. Therefore, the first and second thin film transistors T1 and T2 are simultaneously driven using the central gate line 82a. Simultaneously, scanning signals are sequentially applied to top and bottom portions of the LCD panel 1 with respect to the central gate line 82a. 
A black matrix 96 is formed over the plurality of thin film transistors T, T1 and T2 to correspond to the plurality of gate lines 82, 82a, the plurality of data lines 84 and the plurality of thin film transistors T, T1 and T2. The black matrix 96 is formed to prevent leakage current by shielding the plurality of thin film transistors from irradiation of the incident light. In addition, the black matrix 96 is formed to prevent a light leakage from the backlight unit by shielding an interval space between the plurality of pixel electrodes 94 and the plurality of gate and data lines 82, 82a and 84.
That is, the black matrix 96 includes a first portion 96a corresponding to the first and second thin film transistors T1 and T2 and a second portion 96b corresponding to one of the plurality of thin film transistors except the first and second thin film transistors T1 and T2. In other words, the black matrix 96 has different sizes corresponding to the plurality of thin film transistors T, T1 and T2 with respect to the central gate line 82a such that the first portion 96a is bigger than the second portion 96b. Since the black matrix 96 has different portions between a portion of the central gate line 82a and a portion of the other gate lines 82 except the central gate line 82, it occurs as an image quality defect, such as a moiré phenomenon, and an image quality problem in that the central gate line 82a is prominently shown. More specifically, the moiré phenomenon may be defined as an interference pattern, such as a ripple pattern, having a bigger period than an origin size when at least one pattern having a period in a space view.
Consequently, the moiré phenomenon of the interference pattern adjacent to the central gate line 82a due to a size difference between the first and second portions 96a and 96b of the black matrix 96 may occur, thereby reducing the image quality of the display.